CROSS REFERENCE TO RELATED APPLICATIONS
The present application is related to United States Patent Application Serial No. 07/995,803 entitled, "A Flash Disaster Recovery ROM and Utility to Reprogram Multiple ROMs in the Event of Data Corruption" filed Dec. 23, 1992 by Min Eig Lee, et al., and U.S. patent application Ser. No. 07/885,804 entitled "Multiple Mode standard Parallel Port for a Personal Computer" filed May. 15, 1992 by Clark Buxton et al., both assigned to the same assignee as the assignee of the present application.
1. Field of the Invention
The present invention relates to computer systems and more particularly to a computer system which includes a flash read only memory (or other electrically programmable memory) which contains the instructions for the basic input output system (BIOS); supported by a special purpose interface for switching the mode of operation of a parallel port from a standard peripheral interface, such as a printer interface, to a special purpose interface to enable the BIOS to be executed from an external ROM or another computer connected to the parallel port in the event the flash ROM becomes corrupt.
2. Description of the Prior Art
IBM type PC/AT compatible computers contain a set of routines known as the basic input output system (BIOS) on a ROM chip within the computer. These BIOS routines control the input output functions of the computer's peripheral devices, such as the display, keyboard and disc drives. In particular, these BIOS routines act as an interface to translate various software commands for the peripheral devices from various application programs and the disc operating system (DOS) to commands that are compatible with the hardware. In addition, the BIOS includes routines that either contain information or perform tasks that are fundamental to other aspects of the computer's operation, such as keeping track of the date and the time of day.
Occasionally, the BIOS needs to be updated for various reasons. For example, early BIOS versions did not support 3-1/2 inch floppy disc drives and thus older personal computers which were later equipped with such drives required a BIOS update. There are various other situations which could require a change of the BIOS. For example, existing computer systems may include a version of BIOS that does not support a CD ROM or newer graphic standards. In such situations, it is necessary for the BIOS ROM, normally connected to the motherboard inside the computer housing, to be replaced with a new ROM that contains the updated BIOS if a CD-ROM or enhanced graphics are desired.
When the BIOS requires updating, it is necessary that the computer case be opened and the motherboard removed. Once the motherboard is removed, the ROM chip which contains the BIOS is then replaced with the new ROM chip which contains the updated version of the BIOS. The motherboard is then replaced and the computer case is closed. As such, replacement of the BIOS chip is rather cumbersome and oftentimes is done by a computer technician which can be relatively expensive.